Detail sanders are used for performing specific finishing tasks such as sanding edges adjacent internal walls. To perform such tasks, the tools utilized must be able to have controlled finite movement in a confined area so as to fine sand the desired area without damaging the surface upon which the work is being performed. Various approaches have been taken to perform the difficult task of sanding these internal corners and other hard to reach areas which require fine sanding or abrasion.
Initially, hand sanders were utilized to perform these tasks. U.S. Pat. No. 4,825,597 to Matechuk discloses a corner hand sander which has a sanding surface in the form of a prism having an angle of 90 degrees. Electrically operated tools replaced hand corner sanders similar to the one disclosed above. A common feature among the electrically driven sanders or grinders is that all utilize pivotal or oscillating motion or rotational motion to drive the abrasive pad.
U.S. Pat. No. 4,920,702 to Kloss et al., discloses a portable grinder relying upon pivotal motion by oscillating about a fixed axis which intersects the grinding tool in a central region. The abrasive pad has exposed side edges which are convex in shape such that side edges meet to form at least one corner region having an angle of less than 90 degrees. A similar pear-shaped oscillating abrasive pad for reaching into square corners is described in UK patent 2141620 to Brown.
U.S. Pat. No. 3,190,045 to Zuzelo, discloses an abrasive tool defining an equilateral triangle having three convex sides such that each side is curved in the form of an arc centered on the opposing vertex. The tool rotates about a central axis and has 3 corners which form approximately 90.degree. angles for grinding or polishing into square corners.
An alternative approach is disclosed in U.S. Pat. No. 3,160,995 to Damuski, Jr. in which a corner sander has an oscillating or reciprocating sector-shaped abrasive pad. The pad contains a pair of radiant side edges which move through a total angle just slightly less than the 90 degree angle of the corner to be finished.
U.S. Pat. No. 2,350,098 to Decker discloses an oscillating sander which has a sanding head which has an abrasive pad which is driven about an angle transverse to and at a right angle with the motor drive shaft.
U.S. Pat. No. 2,734,139 to Murphy discloses an electrically operated eraser which utilizes spaced magnetic poles and an adjacent armature movable therebetween for actuating the tool. A drive pin is connected to the armature and a fulcrum to shiftably move the eraser. In this configuration, the armature reciprocates between the two poles by means for magnetizing the poles.
The present invention incorporates many of the known benefits of detail sanders while improving the mechanism utilized for oscillatingly driving the abrasive pads about a pivot axis.